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Abstract:

An electromechanical joining module for applying a linear force to a
joining element, includes a stator, which represents the stationary part
of the joining module, a tappet, which can be linearly extended out of
the stator and which has an outer tappet end, and a force transducer for
detecting forces that are applied to the joining element during the
operation of the tappet end. The force transducer is attached in the area
of the tappet end and has sensor electronics for wirelessly transmitting
measurement data by means of near-field and far-field telemetry.

Claims:

1. Electromechanical joining module for applying a linear force onto a
joining body, comprising a stator, which constitutes the fixed part of
the joining module, a tappet, which can be linearly extended out of the
stator, with an outer tappet end and also a force sensor for detecting
forces which are applied onto the joining body during operation by the
tappet end, wherein the force sensor is attached in the region of the
tappet end and has sensor electronics for the wireless transmission of
measurement data by means of near-field or far-field telemetry.

2. Joining module according to claim 1, wherein the force sensor is a
piezoelectric force sensor or comprises a strain gauge.

4. Joining module according to claim 1, comprising a path sensor for
detecting a tappet path or a tappet position.

5. Joining module according to claim 4, wherein during use, the path
sensor can determine the distance to a joining body onto which the
joining module exerts a force.

6. Joining module according to claim 4, wherein the path sensor is an
incremental, inductive or optical sensor.

7. Joining module according to claim 1, wherein the sensor electronics
are connected to a tappet end which extends over the entire extendible
region of the tappet, wherein close to the tappet coil, the stator has
stator electronics for wirelessly supplying the sensor electronics with
power and for receiving the measurement data by means of near-field
telemetry.

8. Joining module according to claim 7, wherein the tappet coil is
arranged in a groove in the tappet.

9. Joining module according to one of claim 7, wherein the stator
electronics comprise one or a plurality of supply coils which can
generate a magnet alternating field for inducing a voltage in the tappet
coil for supplying power to the sensor electronics.

10. Joining module according to one of claim 7, wherein the stator
electronics have a receiving coil or a receiving antenna receiving
captured measurement values and/or further information such as the status
of the sensor electronics, measurement range, scale information and/or
calibration data.

11. Joining module according to one of claim 1, wherein the sensor
electronics have a transmission module for transmitting the measurement
data by means of far-field telemetry.

[0002] The invention relates to an electromechanical joining module for
applying a linear force onto a joining body, comprising a stator, which
constitutes the fixed part of the joining module, a tappet, which can be
linearly extended out of the stator, with an outer tappet end and also a
force sensor for detecting forces which are applied onto the joining body
during operation by the tappet end.

BACKGROUND

[0003] Electromechanical joining modules are electric motors which apply a
linearly directed force onto a joining body by means of a tappet. Joining
modules for assembly processes in which positive connections are produced
are disseminated in particular. A joining module of this type is known
for example from DE 19721072. This document does not discuss force
measurements, however.

[0004] Joining modules of this type sometimes have force measuring
apparatuses which measure force applied by the joining module onto a
joining body. Measurement data captured in this manner are used for
controlling the processes and/or for quality monitoring.

[0005] In the known joining modules, the force is for the most part
detected in the housing of the joining module. In this case, the
precision is limited due to the bearing friction, force shunts and also
the sluggish mass of the moved parts. Alternatively, a force sensor can
be integrated on the joining body. The cable connection to the force
sensor is mechanically complex however and susceptible to faults and the
lifetime of this cable connection is severely limited.

[0006] A tool for shaping, stamping and injection moulding technology, in
which a force sensor is embedded in the functional surface of the tool,
is known from EP 1057586. This is suitable for determining wear
parameters on the tool, but not for measuring the force when joining as a
whole. To this end, it should especially be avoided that the sensor is
part of the functional surface, in order to prevent measurement errors
due to local inhomogeneities. In addition, this document does not
describe any actuator technology through which the tool moves and through
which force is applied onto the tool. Thus, how the measurement data are
transmitted from a joining body to a stator moving linearly thereto is
also not described.

[0007] In DE 10251387, a press device, which has a torque sensor, is
described. For this, the movement between the moveable part and the
stationary part is a rotation, as a result of which the distance between
both components remains virtually constant. This is a typical joining
module as has been known for a long time. The force on the tool is
determined using the torque sensor indirectly via the spindle pitch.
Unknown variable friction forces of the spindle lead to relatively large
measurement errors. As the sensor does not move translationally, a
telemetric transmission of the measurement data is not a problem.

OBJECTS AND SUMMARY OF INVENTION

[0008] It is the object of the present invention to specify an
electromechanical joining module of the type specified at the beginning,
in which force measurements of the tappet forces can be carried out with
improved precision, whereby the measuring device should be designed for a
long life and can resist a large number of movement cycles undamaged and
without a reduction in quality. In addition, the joining module should
have a simple structure and be low maintenance, and also enable
customer-specific adaptations without additional outlay.

[0009] The object is achieved in that the force sensor is attached in the
region of the tappet end and has sensor electronics for the wireless
transmission of measurement data by means of near-field or far-field
telemetry.

[0010] For transmitting using near-field telemetry, according to the
invention, the sensor electronics are connected to a tappet coil which
extends over the entire extendible region of the tappet. Close to the
tappet coil, the stator has stator electronics for wirelessly supplying
the sensor electronics with power and for receiving the measurement data
by means of near-field telemetry.

[0011] One of the advantages of a joining module according to the
invention is the high precision of the force measurement which can be
carried out therewith, as no error influences can act by means of bearing
friction, force shunts and sluggish mass. The force measurement system is
maintenance-free and the lifetime is substantially independent of the
number of load cycles.

[0012] In particular, this arrangement is simple to realise and can also
be used in an environment where far-field telemetry could cause problems
due to radiation contamination of the environment. Both solutions offer
the advantage, however, that no disruptive cables, which at most could be
damaged, are in the way and that the forces are accommodated in an
unaltered manner in the region of the tappet end, close to the force
developing surfaces, without force shunts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the following, the invention is explained in more detail with
reference to the drawings. In the figures

[0014] FIG. 1 shows a schematic side view of a joining module according to
the invention in (a) the retracted state and (b) in the extended state;

[0015] FIG. 2 shows a schematic illustration according to the invention of
the joining module in the region of the tappet in the extended state;

[0016] FIG. 3 shows an illustration of the tappet according to the
invention (a) with tappet coil and (b) a detailed view of the tappet
coil;

[0017] FIG. 4 shows a cross section of the tappet in the region of the
stator electronics;

[0019] The FIG. 1 shows an electromechanical joining module 1 comprising a
stator 2 which constitutes a fixed part of the joining module 1 and a
tappet 3 which can be moved in a linear direction out of the stator 2.
FIG. 1a shows the joining module 1 in the retracted state, FIG. 1b in a
state with extended tappet 3.

[0020] The tappet 3 has an outer end 4 on which a tool receptacle 6 can be
attached. According to the invention, a force sensor 5, which can measure
the force which acts from the tappet end 4 during use, is located in the
region of the tappet end 4. This force sensor 5 has sensor electronics 7
for the wireless transmission of measurement data by means of near-field
or far-field telemetry.

[0021] In the following, the transmission by means of near-field telemetry
is described in FIGS. 2-5.

[0022] FIG. 2 shows an extended tappet 3 in a stator 2 of the joining
module 1 with force sensor 5 which is attached on the tappet end 4
according to the invention, between tool receptacle 6 and tappet 3 in
this illustration.

[0023] According to the invention, the force sensor 5 has sensor
electronics 7 for wireless transmission of measurement data by means of
near-field telemetry. These sensor electronics 7 are connected to a
tappet coil 8 which extends over the entire extendible region of the
tappet 3. Preferably, as shown in FIGS. 3b and 5 for example, this tappet
coil 8 is arranged in a groove 10 in the tappet 3. Close to the tappet
coil 8, the stator 2 has stator electronics 9 for wirelessly supplying
the sensor electronics 7 with power and for receiving the measurement
data by means of near-field telemetry.

[0024] In this arrangement according to the invention, these stator
electronics 9 comprise one or a plurality of supply coils 11 which can
generate a magnet alternating field. Thus, a voltage is induced in the
tappet coil 8, as a result of which the sensor electronics 7 are supplied
with power. In addition, in this manner, sensor relevant data can also be
sent to the sensor electronics 7 which are used for measurement by means
of the force sensor 5, such as for example the sensitivity of the sensor.
It is advantageous in this connection if the sensor electronics 7
comprise a data memory 14 for storing such measurement-relevant data.

[0025] In addition, the stator electronics 9 have a receiving coil or a
receiving antenna 12 for receiving captured measurement values and/or
further information such as the status of the sensor electronics,
measurement range, scale information and/or calibration data.

[0026] FIG. 3a shows a tappet 3 according to the invention with tappet
coil 8, whereby FIG. 3b shows the tappet coil 8 arranged in the groove 10
in a more detailed illustration. In this illustration in FIG. 3b, the
stator electronics 9 are illustrated in a central region of the tappet 3
overlapping the tappet coil 8.

[0027] FIG. 4 shows a cross section of the tappet 3 in the region of the
stator electronics 9. It can be seen from this illustration that the
stator electronics 9 with the stator supply coil(s) 11 are arranged close
to the tappet coil 8 independently of the tappet position. FIG. 5 is a
detailed view of FIG. 4 in the region of the coils. The illustration
shows the closely opposite, contactlessly arranged primary and secondary
windings, namely the stator supply coil 11 and the receiving coil 12 as
primary windings and the tappet coil 8 on the tappet 3 as secondary
winding.

[0028] It has proven advantageous to transmit the measurement values by
electromagnetic coupling via a modulated carrier by means of phase
modulation (PSK modulation) from the tappet coil 8 to the receiving coil
12, a carrier of approx. 13.56 MHz or approx. 27.1 MHz being used. In
addition to the measurement values, further status information can be
transmitted from the sensor electronics 9 to the stator 2, such as
information about the force sensor, measurement ranges, scale
information, calibration data, etc. The data are preferably transmitted
in a digitised manner.

[0029] A carrier frequency of 119 to 135 kHz is used for the power
transmission. The signals for the energy transmission can also be
modulated in order to transmit control information to the sensor
electronics 9. A phase modulation (PSK modulation) is likewise used as
modulation method. To adapt the transmitted power, the carrier frequency
is changed at the stator in the range from 119 to 135 kHz.

[0030] In a preferred configuration, the force sensor 5 is a piezoelectric
force sensor.

[0031] In particular, as shown in FIG. 2 for example the joining module 1
according to the invention can additionally have a path sensor 15 for
detecting a tappet path or a tappet position. During use, this can for
example determine the distance to a joining body onto which the joining
module exerts a force. The path sensor 15 can preferably be an
incremental, inductive or optical sensor.

[0032] Alternatively to near-field telemetry, the joining module 1
according to the invention can be provided with sensor electronics 7
which have a transmission module for transmitting the measurement data by
means of far-field telemetry. In this case, the sensor electronics 7 can
comprise a rechargeable battery. This rechargeable battery can for
example likewise be charged from the stator, for example if the tappet 3
is completely retracted, by means of contacts correspondingly attached
thereto. A regular exchange of the rechargeable battery would also be
possible. The advantage of such an arrangement is that the measurement
data can be sent directly to an analysis unit at any desired location for
further processing and/or for controlling the joining module 1, without
it being necessary to forward measurement data from the same to a control
unit.